Pneumatic piston engines



Dec. 6, 1960 H. HERRMANN 2,963,005

PNEUMATIC PISTON ENGINES Filed sept. 1s. 1958 INVENTOR HEL MT Him? /w/mw 2,963,005 PNEUMATIC PlsroN ENGINES Helmut Herrmann, Altlunen, Westphalia, Germany, assrgnor to Gewerkschaft Eisenhuette Westfalia, Wethmar, near Lunen, Westphalia, Germany, a corporation of Germany Filed Sept. 18, 1958, Ser. No. 761,790

Claims priority, application Germany Oct. 11, 1957` 6 Claims. (Cl. 121-29) This invention relates to pneumatic piston engines. More particularly, it relates to pneumatic piston engines having means for pneumatically arresting the piston working strokes.

Free piston engines employed to impart vibration to vibrating apparatus are commonly provided with air buffers for arresting the working strokes of the engine piston. The air buer can be provided by a cylinder extension which receives a buffering piston eiective to alternately compress and expand air within the cylinder extension and also effective to arrest the working stroke of the engine in response to the compression. Heat is generated due to the compression and due to friction. Heat is also generated by the operation of a control valve mechanism commonly used on such engines. The engine control valve positioning means commonly includes a conduit which communicates with the air butler and whose function it is to allow compressed air to reciprocate in the conduit in synchronism with compression and expansion of air in the air buffer. This reciprocating flow in the conduit generates heat. The generation of heat inthe air buffers and conduits makes use of the engines dangerous in some services such as for example, when employed in underground mines. Accordingly, it is a principal object of the invention to provide means for suitably and conveniently removing heat from air buers and the conduits of pneumaticengines.

The manner in which this and other objects of the invention are attained will beunderstood from the following description taken together with the accompanying drawing.

In the drawing:

Fig. l is a cut-away view, partly in section of a free piston engine including the improvement of the invention; and

Fig. 2 is a cross-section taken along line 2-2 in Fig. 1.

.'The desired buffering action of the engine piston of a pneumatic engine is obtained by providing a chamber for containing a body of gas for alternate compression and expansion of gas, means effective to alternately compress and expand the gas in synchronism with the engine piston so that the gas within the chamber is compressed during the engine piston working stroke and expanded during the engine piston return stroke, and means responsive to compression of the gas within the chamber and effective to arrest the motion of the engine. piston on its working nited States Patent stroke. The engine is provided with control valve means v for alternately communicating the engine cylinderwith an intake port and an exhaust port, and the control valve positioning means includes a conduit which is in flow communication with the buffering chamber. Air or other gas within the conduit reciprocates therein in synchronism with compression and expansion occurring in the engine cylinder and this reciprocating flow aids in positioning of the control valve.

According to the invention, either or both the buffering chamber and the conduit of the valve positioning means is provided with a jacket through which a cooling medium fice can be circulated to withdraw heat developed in these parts of the engine. Preferably, both the buffering chamber and conduit are provided with a jacket and the jackets are interconnected for series flow of cooling medium therethrough. Conveniently, the jackets are connected in series and the compressed air supplied to the engine is ilowed through the jackets. When operated in this manner, the compressed gas provides the desired cooling, and further, the compressed gas is heated somewhat so that excessive cooling as might cause freezing of the engine is prevented. In general, in the case of compressed air engines, filling cannot go below as otherwise there is danger of excessive cooling upon the expansion. This can in turn result in freezing of the engine. lf, however, in accordance with the invention, the compressed air is preheated by passage through the jackets, before introduction into the engine cylinder, then too much cooling is prevented, even in the case of filling below 80% and correspondingly greater expansion.Y

In the embodiment shown in the drawing, the pneumatic engine comprises an engine piston 11 which is a double acting piston and an engine cylinder 10. A control valve 17, including valve assembly 16 is provided for alternately communicating each of the cylinder working spaces 14 and 15 with one of the intake ports 3 or 4 and the exhaust port 5.

To provide bulfering action for the engine pistons, the piston 11 is provided with piston extensions 8 and 9 and the cylinder 10 is provided with cylinder extensions 6 and 7 which slideably receive the piston extensions. The cylinder extensions 6 and 7, together with the engine end walls 31 and 32, respectively, provide chambers 12 and 13 in which a gas can be alternately compressed and expanded in synchronism with the action of the engine so that as an incident of each working stroke of the piston, gas Yis compressed in one of the chambers and the compression is effective to elastically arrest the working s troke.`

The control valve 17 is positioned by operation of the piston-cylinder arrangements 18 and 19. These pistoncylinder arrangements are installed so that the cylinders 18a and 19a thereof communicate with chambers 12 and 13, respectively, by means of conduits 20 and 21, respectively. Thus, as gas is alternately compressed and expanded in the buffering chambers, gas is caused to iiow in a reciprocating manner in the conduits 20 and 21. The How through the conduits 20 and21 generates a large amount of heat.

Gas is supplied to the buffering chambers 12 and 13 from space 33 within the engine cylinder 10 and which communicates with the buffering chambers via passageways 34 and 35. The outlets of passageway 35 to the buiering chambers 12 and 13 are provided with check valves 36 which permit gas to ow into the buffering chambers but prevent outward flow of gas from the chambers. Thus, by operation of the check valves, a body of gas is maintained within the buffering chambers and gas which leaks from the chambers is replenished from gas contained in space 33. The space 33 is advantageously in communication with a source of compressed gas which can be the compressed gas supplied for operation of the engine or compressed gas at some lower pressure. Since a body of gas is maintained in the buffer ing chambers and alternately expands and is compressed in these chambers, heating results. Heat is also generated due to friction between moving parts of the engine.

According to the invention, the buiering chambers 12 and 13 are provided, respectively, with jackets 23 and 24. Jacket 23 is provided with inlet 29a, an outlet 37 and a partition wall 25. The partition wall 25 insures that the ow path through the jacket will be from the inlet around the cylinder and. to the outlet. The jacket 24 is of similar construction and includes inlet 28a and outlet 38. The inlet connections to the chamber jackets are connected with compressed air inlet 22 by pipes 28 and 29. The outlets 38 and` 37 of the chamber jackets are connected, respectively, with the engine intake ports 3 and 4 by pipes 26 and 27, respectively. The conduits 20 and 21, which communicate buffering chamber pressure to valve positioning piston-cylinder arrangements 1'8 and 19, are disposed respectively within the pipes 26 and *27,l and thus these pipes are jackets for the conduits.

In operation of the engine, air inlet 22 is connected to a compressed gas source (not shown) and compressed gas flows into lines 28 and 29 and then in parallel through the chamber jackets 12 and 13'ar1d the pipes 26 and 27 to the intake ports 4 and 3. Thus, the compressed gas for the engine is employed to effect cooling of the buffering chambers and the conduits 20 and 21, lwhich form part of the valve positioning means and have flowing therein a gas in a reciprocating manner.

I- claim:

y 1. In a pneumatic piston yengine including an engine piston and cylinder and having means for pneumatically buffering the working stroke Vof Ythe engine piston, said means including a chamber for containing a body of gas for alternate compression and expansion, means effective to alternately compress and expand gas contained within said chamber in synchronism with the engine piston compressing the gas on the working stroke and expanding the gas on the return stroke, means responsive to said compression and effective to arrest the motion of the engine pisto-n on its working stroke, control valve means for alternately communicating said cylinder with an intake port and an exhaust port, control valve positioni-ng means including a conduit in flow communication with said chamber for positioning said control valve means with reciprocating ow in said conduit in synchronism with compression and expansion n said cylinder, the improvement which comprises means defining a jacket for said chamber and means defining a jacket for said conduit, means interconnecting said jackets for series ow therethrough, inlet means to one of said jackets, loutlet means from the other of said jackets, means communicating said outlet means with said intake port, whereby compressed gas for driving said engine can be flowed serially through said jackets to cool said chamber and said conduit and means for passing said compressed gas through said jacket before the same enters the engine cylinder, whereby the gas is heated somewhat and excessive cooling, as might cause freezing of the engine, is prevented.

2. A pneumatic piston engine according to claim 1, said i-nlet means being connected to the chamber jacket and the outlet means being connected to the conduit jacket.

3. In a pneumatic piston engine including an engine piston and cylinder and having means for pneumatically buffering the working stroke of the engine piston, said means including a chamber for containing a body of gas for alternate compression and expansion, means effective to alternately compress and expand gas contained within said chamber in synchronism with the engine piston compressing the gas on the working stroke and expanding the gas on the return stroke, means responsive to said compression and effective to arrest the motion of the engine piston on its working stroke, the improvement which comprises means dening a jacket for said chamber, means for supplying a cooling medium to said jacket whereby heat developed during said compression and expansion can be withdrawn and means for passing said compressed gas through said jacket before the same enters the engine cylinder, whereby the gas is heated somewhat and excessive cooling, as might cause freezing of the engine, is prevented.

4. In a pneumatic piston engine including an engine piston and cylinder and having means for pneumatically buffering the Working stroke of the engine piston, said means includnig a chamber for containing a body of gas for alternate compression and expansion, means effective to `alternately compress and expand gas contained within said chamber in synchronism with the engine piston compressing the gas on the working stroke and expanding the gas on the return stroke, means responsive to said compression and effective to arrest the motion of the engine piston on its lworking stroke, the 'improvement which comprises means defining a jacket for s'aid chamber, means for supplying compressed gas to said jacket, means for receiving compressed gas from said jacket and conveying it to said cylinder for use as compressed gas for actuating said piston and means for passing said compressed gas through said jacket before the same enters the engnie cylinder, whereby the gas is heated somewhat and excessive cooling, as might cause freezing of the engine, is prevented.

5. In a pneumatic piston engine including an engine piston and cylinder' and having means for pneumatically buffering the working stroke of the engine piston, said means including a chamber for containing a body of gas for alternate compression and expansion, means effective to alternately compress and expand gas contained within said chamber in synchronism with the engine piston compressing the gas on the working stroke and expanding the gas on the return stroke, means responsive to said compression and effective to arrest the motion of the engine piston on its working stroke, control valve means for alternately communicating said cylinder with an intake port and an exhaust port, control valve positioning means includingV a conduit in flow communication with said chamber for positioning said control valve means with reciprocating flow in said conduit in synchronism with compression and expansion in said cylinder, the improvement which comprises means defining a jacket for said conduit and means for supplying a cooling medium to said jacket whereby heat developed in said conduit can be withdrawn.

6. A pneumatic piston engine according to claim 5, means for supplying compressed gas to said jacket as cooling medium, and 'means for receiving compressed gas from said jacket and conveying it to said cylinder for use as compressed gas for actuating said piston whereby the gas is heated somewhat and excessive cooling, as might cause freezing of'said cylinder, is prevented.

References Cited in the file of this patent UNITED STATES PATENTS 1,488,171 Savidge Mar. 25, 1924 2,751,144 Troendle June 16, 1956 2,876,191 Herrmann Jan. 6, 1959 FOREIGN PATENTS 810,898 Germany Aug. 13, 1951 L A... "..e- 

